Heat exchanger shell and tube pdf

Posted on Monday, June 7, 2021 6:57:17 PM Posted by Karenina E. - 07.06.2021 and pdf, management pdf 4 Comments

heat exchanger shell and tube pdf

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The design of heat exchanger is needed to overcome the problem of water availability with temperature that suits the needs of the Test Stand.

Design & Analysis of Shell & Tube Type Heat Exchanger

TEMA designations for shell- and -tube heat exchangers. A disadvantage of this design isthat since the bundle is fixed to theshell and cannot be removed, the outsidesof the tubes cannot be cleanedmechanically. Thus, its application islimited to clean services on the shellside. However, if a satisfactory chemicalcleaning program can be employed,fixed-tubesheet constructionmay be selected for fouling serviceson the shellside.

In the event of a large differentialtemperature between the tubes and the shell, the tubesheets will be unableto absorb the differential stress,thereby making it necessary to incorporatean expansion joint. This takesaway the advantage of low cost to asignificant extent. As the name implies, thetubes of a U-tube heat exchanger Figure 3 are bent in the shape of aU. There is only one tubesheet in a U-tube heat exchanger. However, thelower cost for the single tubesheet isoffset by the additional costs incurredfor the bending of the tubes and thesomewhat larger shell diameter dueto the minimum U-bend radius , makingthe cost of a U-tube heat exchangercomparable to that of a fixedtubesheetexchanger.

The advantage of a U-tube heatexchanger is that because one end isfree, the bundle can exp and or contractin response to stress differentials. In addition, the outsides of thetubes can be cleaned, as the tube bundlecan be removed. The disadvantage of the U-tubeconstruction is that the insides of thetubes cannot be cleaned effectively,since the U-bends would require flexible-enddrill shafts for cleaning.

Thus, U-tube heat exchangers shouldnot be used for services with a dirtyfluid inside tubes. Floating head. The floating-headheat exchanger is the most versatiletype of STHE, and also the costliest. Fixed-tubesheet heat exchanger. U-tube heat exchanger.

Thispermits free expansion of the tubebundle, as well as cleaning of boththe insides and outsides of the tubes. Thus, floating-head SHTEs can beused for services where both theshellside and the tubeside fluids aredirty — making this the st and ard constructiontype used in dirty services,such as in petroleum refineries.

There are various types of floating-headconstruction. The floating-head cover is securedagainst the floating tubesheet by boltingit to an ingenious split backingring. This floating-head closure is locatedbeyond the end of the shell and contained by a shell cover of a largerdiameter. To dismantle the heat exchanger,the shell cover is removedfirst, then the split backing ring, and then the floating-head cover, afterwhich the tube bundle can be removedfrom the stationary end.

In the TEMA T construction Figure5 , the entire tube bundle, includingthe floating-head assembly, canbe removed from the stationary end,since the shell diameter is larger thanthe floating-head flange. The floatingheadcover is bolted directly to thefloating tubesheet so that a split backingring is not required.

The advantage of this constructionis that the tube bundle may be removedfrom the shell without removingeither the shell or the floatingheadcover, thus reducing maintenancetime.

This design is particularlysuited to kettle reboilers having adirty heating medium where U-tubescannot be employed. Due to the enlargedshell, this construction has thehighest cost of all exchanger types. Classificationbased on serviceBasically, a service may be singlephase such as the cooling or heatingof a liquid or gas or two-phase suchas condensing or vaporizing.

Sincethere are two sides to an STHE, thiscan lead to several combinations ofservices. The following nomenclature isusually used: Heat exchanger: both sides singlephase and process streams that is,not a utility. Cooler: one stream a process fluid and the other cooling water or air. Heat er: one stream a process fluid and the other a hot utility, such assteam or hot oil. Condenser: one stream a condensingvapor and the other cooling wateror air.

Chiller: one stream a processfluid being condensed at sub-atmospherictemperatures and the other aboiling refrigerant or process stream. Reboiler: one stream a bottomsstream from a distillation column and the other a hot utility steam or hotoil or a process stream. This article will focus specificallyon single-phase applications. Design dataBefore discussing actual thermaldesign, let us look at the data thatmust be furnished by the process licensorbefore design can begin This is required for gases,especially if the gas density is notfurnished; it is not really necessaryfor liquids, as their properties do notvary with pressure.

This is a very importantparameter for heat exchanger design. Generally, for liquids, a value of0. A higher pressure drop is usually warrantedfor viscous liquids, especiallyin the tubeside.

For gases, the allowedvalue is generally 0. If this is not furnished, thedesigner should adopt values specifiedin the TEMA st and ards or basedon past experience. These include viscosity,thermal conductivity, density, and specific heat, preferably at both inlet and outlet temperatures.

Viscositydata must be supplied at inlet and outlet temperatures, especially forliquids, since the variation with temperaturemay be considerable and isirregular neither linear nor log-log.

The duty specifiedshould be consistent for both theshellside and the tubeside. If notfurnished, the designer can choosethis based upon the characteristics ofthe various types of construction describedearlier. In fact, the designer isnormally in a better position than theprocess engineer to do this.

It is desirable tomatch nozzle sizes with line sizes toavoid exp and ers or reducers. However,sizing criteria for nozzles are usuallymore stringent than for lines, especiallyfor the shellside inlet. Consequently,nozzle sizes must sometimesbe one size or even more in exceptionalcircumstances larger than thecorresponding line sizes, especiallyfor small lines.

Tube sizeis designated as O. Some plant owners have apreferred O. Many plant owners prefer to st and ardizeall three dimensions, againbased upon inventory considerations. Thisis based upon tube-bundle removal requirements and is limited by crane capacities. Such limitations apply only toexchangers with removable tube bundles,namely U-tube and floating-head. Thus, floating-headheat exchangers are often limited to ashell I.

Ifthe tubes and shell are made of identicalmaterials, all components shouldbe of this material. Thus, only theshell and tube materials of constructionneed to be specified. However, ifthe shell and tubes are of differentmetallurgy, the materials of all principalcomponents should be specifiedto avoid any ambiguity. The principalcomponents are shell and shellcover , tubes, channel and channelcover , tubesheets, and baffles.

Tube sheets may be lined or clad. Theseinclude cycling, upset conditions, alternativeoperating scenarios, and whether operation is continuous orintermittent. Heat -transfercoefficient and pressure drop bothvary with tubeside velocity, the lattermore strongly so. A good design willmake the best use of the allowablepressure drop, as this will yield thehighest heat-transfer coefficient.

If all the tubeside fluid were toflow through all the tubes one tubepass , it would lead to a certain velocity. Usually, this velocity is unacceptablylow and therefore has to be increased. By incorporating pass partitionplates with appropriate gasketing in the channels, the tubeside fluidis made to flow several times througha fraction of the total number of tubes. Thus, in a heat exchanger with tubes and two passes, the fluid flowsthrough tubes at a time, and thevelocity will be twice what it wouldbe if there were only one pass.

Thenumber of tube passes is usually one,two, four, six, eight, and so on. Viscosity influences the heat-transfercoefficient in two opposing ways— as a parameter of the Reynoldsnumber, and as a parameter of Pr and tlnumber. Thus, from Eq. Similarly,the heat-transfer coefficient isdirectly proportional to thermal conductivityto the 0. These two facts lead to some interestinggeneralities about heat transfer. A high thermal conductivity promotesa high heat-transfer coefficient.

Hydrogen is an unusual gas, becauseit has an exceptionally highthermal conductivity greater thanthat of hydrocarbon liquids. Thus,its heat-transfer coefficient is towardthe upper limit of the rangefor hydrocarbon liquids. The range of heat-transfer coefficientsfor hydrocarbon liquids isTie Rods and SpacersFloating Tube sheet Shell Cover Heat -transfer coefficientThe tubeside heat-transfer coefficientis a function of the Reynoldsnumber, the Pr and tl number, and the tube diameter.

These can be brokendown into the following fundamentalparameters: physicalproperties namely viscosity, thermalconductivity, and specific heat ;tube diameter; and , very importantly,mass velocity. The variation in liquid viscosity isquite considerable; so, this physicalproperty has the most dramatic effecton heat-transfer coefficient. The large variation in the heat-transfercoefficients of hydrocarbon gases isattributable to the large variation inoperating pressure.

As operating pressurerises, gas density increases. Pressuredrop is directly proportional tothe square of mass velocity and inverselyproportional to density.

Therefore,for the same pressure drop, ahigher mass velocity can be maintainedwhen the density is higher. Thislarger mass velocity translates into ahigher heat-transfer coefficient. Pressure dropMass velocity strongly influencesthe heat-transfer coefficient. For turbulentflow, the tubeside heat-transfercoefficient varies to the 0.

Thus, with increasingmass velocity, pressure drop increasesmore rapidly than does theheat-transfer coefficient.

Consequently,there will be an optimum mass velocityabove which it will be wastefulto increase mass velocity further. Furthermore, very high velocitieslead to erosion. However, the pressuredrop limitation usually becomescontrolling long before erosive velocitiesare attained. The minimum recommendedliquid velocity insidetubes is 1.

Pressure drop is proportional tothe square of velocity and the totallength of travel. Thus, when the numberof tube passes is increased for agiven number of tubes and a giventubeside flow rate, the pressure droprises to the cube of this increase.

Inactual practice, the rise is somewhatless because of lower friction factorsat higher Reynolds numbers, so theexponent should be approximately2.

Tube side pressure drop rises steeplywith an increase in the number of tubepasses. Consequently, it often happensTable 1. Heat exchanger service for Example 1.

BROCHURE shell & tube heat exchanger (pdf)

Abstract:- Shell and Tube heat exchangers are having special importance in boilers, oil coolers, condensers, pre-heaters. They are also widely used in process applications as well as the refrigeration and air conditioning industry. The robustness and medium weighted shape of Shell and Tube heat exchangers make them well suited for high pressure operations. The basic configuration of shell and tube heat exchangers, the thermal analysis and design of such exchangers form an included part of the mechanical, thermal, chemical engineering scholars for their curriculum and research activity. Heat exchangers are used to transfer thermal energy between two or more media and widely applicable to chemical industries, food industries, power engineering and so on. The shell.

design of shell and tube heat exchanger (single phase)

TEMA designations for shell- and -tube heat exchangers. A disadvantage of this design isthat since the bundle is fixed to theshell and cannot be removed, the outsidesof the tubes cannot be cleanedmechanically. Thus, its application islimited to clean services on the shellside. However, if a satisfactory chemicalcleaning program can be employed,fixed-tubesheet constructionmay be selected for fouling serviceson the shellside. In the event of a large differentialtemperature between the tubes and the shell, the tubesheets will be unableto absorb the differential stress,thereby making it necessary to incorporatean expansion joint.

A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink , which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant. There are three primary classifications of heat exchangers according to their flow arrangement.

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Shell and Tube

There are various types of heat exchangers used in process piping. Shell and tube heat exchanger is the most widely used heat exchanger and are among the most effective means of heat exchange. Shell and tube heat exchanger is a device where two working fluids exchange heats by thermal contact using tubes housed within a cylindrical shell.

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The characteristics of flow and heat transfer of shell-and-tube heat exchangers with overlapped helical baffles STHXsHB were illustrated through a theoretical analysis and numerical simulation. The ideal helical flow model was constructed to demonstrate parts of the flow characteristics of the STHXsHB, providing theoretical evidence of short-circuit and back flows in a triangular zone. The numerical simulation was adopted to describe the characteristics of helical, leakage, and bypass streams. In a fully developed section, the distribution of velocity and wall heat transfer coefficient has a similar trend, which presents the effect of leakage and bypass streams. The short-circuit flow accelerates the axial velocity of the flow through the triangular zone. Moreover, the back flow enhances the local heat transfer and causes the ascent of flow resistance. This study shows the detailed features of helical flow in STHXsHB, which can inspire a reasonable optimization on the shell-side structure.


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